The present invention relates to a chemical mechanical polishing pad.
In recent years, a chemical mechanical polishing method (generally abbreviated as “CMP”) has attracted attention as a polishing method that can form a surface having excellent flatness on a silicon substrate or a silicon substrate on which interconnects, electrodes, and the like are formed (hereinafter referred to as “semiconductor wafer”) in the production of semiconductor devices, for example. The chemical mechanical polishing method polishes a polishing target surface while causing the polishing target surface to slidingly come in contact with a chemical mechanical polishing pad and supplying a chemical mechanical polishing aqueous dispersion (aqueous dispersion in which abrasive grains are dispersed; slurry) to the surface of the chemical mechanical polishing pad. In the chemical mechanical polishing method, the polishing results are significantly affected by the properties and the like of the chemical mechanical polishing pad. Various chemical mechanical polishing pads have been proposed.
For example, a polyurethane foam that contains minute bubbles is used as the chemical mechanical polishing pad, and the polishing target surface is polished in a state in which the chemical mechanical polishing aqueous dispersion is held in pores formed in the surface of the chemical mechanical polishing pad (see JP-A-11-70463, JP-A-8-216029, and JP-A-8-39423, for example).
When using such a chemical mechanical polishing pad, since the slurry is supplied to the polishing pad in a state in which a semiconductor wafer is pressed against the surface of the polishing pad, it is difficult to remove the semiconductor wafer from the surface of the polishing pad after polishing without applying load. Moreover, the adhesion between the polishing pad and a polishing platen on which the polishing pad is placed decreases due to removal of the semiconductor wafer from the surface of the polishing pad so that a friction occurs between the polishing pad and a dresser or the semiconductor wafer. As a result, the edge of the polishing pad may be removed from the polishing platen, or a polishing layer of the polishing pad may be removed from a cushion layer. Therefore, removal of the semiconductor wafer, breakage of the polishing pad, or abnormal wear of the surface of the polishing pad occurs so that the durability and the polishing capability of the polishing pad deteriorate.
In order to solve this problem, JP-A-2006-196836 discloses technology that suppresses removal problems by utilizing a polishing pad that has an outer periphery lower than the polishing surface.
However, surface defects (scratches) on a semiconductor wafer (polishing target) may not be sufficiently reduced by the technology disclosed in JP-A-2006-196836.